Conventionally, before being released to the open air, the exhaust gases may be purified by means of a particulate filter like the one shown in FIGS. 1 and 2, known in the prior art.
A particulate filter 1 is shown in FIG. 1 in a transverse cross section, along the plane of section B-B shown in FIG. 2, and in FIG. 2 in a longitudinal cross section along the plane of section A-A shown in FIG. 1.
The particulate filter 1 conventionally comprises at least one filter body 3, inserted in a metal housing 5. The filter body 3 results from the assembly and machining of a plurality of blocks 11, referenced 11a-11i. 
To fabricate a block 11, a ceramic material (cordierite, silicon carbide, etc.) is extruded to form a porous honeycomb structure. The extruded porous structure conventionally has the shape of a rectangular parallelepiped, comprising four longitudinal edges 11′, extending along an axis D-D between two substantially square upstream 12 and downstream 13 faces at which a plurality of adjacent, square section, straight channels 14 terminate, parallel to the axis D-D. The channels are formed by the interpenetration of two sets of plane and parallel partitions, the partitions of the first set being perpendicular to the partitions of the second set. The four partition portions bounding a channel 14 constitute a side wall 22 of this channel. Conventionally, all the partitions of the two sets have the same thickness, that is, the side wall 22 of any channel 14 has a constant thickness.
After extrusion, the extruded porous structures are alternately plugged on the upstream face 12 (outlet channels 14s) or on the downstream face 13 (inlet channels 14e), by upstream 15s and downstream 15e plugs, respectively, as is well known. At the opposite end of the outlet 14s and inlet 14e channels from the upstream 15s and downstream 15e plugs, respectively, the outlet 14s and inlet 14e channels terminate outwardly in outlet 19s and inlet 19e openings, respectively, extending on the downstream 13 and upstream 12 faces, respectively.
Each channel 14 thereby defines an internal volume 20 bounded by the side wall 22, a plug 15s or 15e, and an outwardly terminating opening 19s or 19e. 
The set of external faces 15′ of the channels located at the periphery of a block 11, or “peripheral channels” 14p, forms an external surface 16 of the block 11 (see FIG. 3). Because of the substantially square transverse cross section of the block 11, the external surface 16 comprises four faces 16a-16d, perpendicular in pairs.
The blocks 11a-11i are assembled together by bonding using seals 27 of ceramic cement generally consisting of silica and/or silicon carbide and/or aluminum nitride. The assembly thus formed can then be machined to obtain, for example, a round cross section. Thus the external blocks 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h have an external face that is rounded by machining.
This produces a cylindrical filter body 3 with axis C-C, which can be inserted into the housing 5, a peripheral seal 28, gastight to the exhaust gases, being arranged between the external filter blocks 11a-11h and the housing 5.
As indicated by the arrows shown in FIG. 2, the flow F of exhaust gases enters the filter body 3 via the openings 19e of the inlet channels 14e, passes through the filtering side walls of these channels to join the outlet channels 14s, and then escapes to the exterior via the openings 19s. 
After a certain period of use, the particulates, or “soot”, accumulated in the inlet channels 14e of the filter body 3 impair the performance of the engine. This is why the filter body 3 must be regenerated regularly, for example every 500 kilometers. The regeneration, or “unclogging”, consists in oxidizing the soot by heating it to a temperature permitting its ignition.
During the regeneration phases, the exhaust gases transport downstream all the heat energy liberated by the combustion of the soot. Moreover, since the soot is not uniformly deposited in the various channels, the combustion zones are not uniformly distributed in the filter body 3. Finally, the peripheral zones of the filter body 3 are cooled, via the metal housing 5, by the surrounding air.
As a result, the temperature differs according to the zones of the filter body 3 and does not vary uniformly. The nonuniformity of the temperatures within the filter body 3 and the differences in the nature of the materials used for the filter blocks 11a-11i on the one hand, and for the seals 27 on the other, generate high amplitude local stresses, which can cause local breakage or cracks. In particular, the local stresses at the interfaces between the blocks 11a-11h and the housing 5, and between the blocks 11a-11i and the seals 27, can cause cracks in the blocks 11a-11i thereby shortening the service life of the particulate filter 1.